Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commit8ca5662

Browse files
committed
Fix potential pointer overflow in xlogreader.c.
While checking if a record could fit in the circular WAL decodingbuffer, the coding from commit3f1ce97 used arithmetic that couldoverflow. 64 bit systems were unaffected for various technical reasons,which probably explains the lack of problem reports. Likewise for 32bit systems running known 32 bit kernels. The systems at risk ofproblems appear to be 32 bit processes running on 64 bit kernels, withunlucky placement in memory.Per complaint from GCC -fsanitize=undefined -m32, while testingvariations of 039_end_of_wal.pl.Back-patch to 15.Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>Reviewed-by: Robert Haas <robertmhaas@gmail.com>Discussion:https://postgr.es/m/CA%2BhUKGKH0oRPOX7DhiQ_b51sM8HqcPp2J3WA-Oen%3DdXog%2BAGGQ%40mail.gmail.com
1 parenta09aa18 commit8ca5662

File tree

1 file changed

+37
-9
lines changed

1 file changed

+37
-9
lines changed

‎src/backend/access/transam/xlogreader.c

Lines changed: 37 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -457,18 +457,37 @@ XLogReadRecordAlloc(XLogReaderState *state, size_t xl_tot_len, bool allow_oversi
457457
if (state->decode_buffer_tail >=state->decode_buffer_head)
458458
{
459459
/* Empty, or tail is to the right of head. */
460-
if (state->decode_buffer_tail+required_space <=
461-
state->decode_buffer+state->decode_buffer_size)
460+
if (required_space <=
461+
state->decode_buffer_size-
462+
(state->decode_buffer_tail-state->decode_buffer))
462463
{
463-
/* There is space between tail and end. */
464+
/*-
465+
* There is space between tail and end.
466+
*
467+
* +-----+--------------------+-----+
468+
* | |////////////////////|here!|
469+
* +-----+--------------------+-----+
470+
* ^ ^
471+
* | |
472+
* h t
473+
*/
464474
decoded= (DecodedXLogRecord*)state->decode_buffer_tail;
465475
decoded->oversized= false;
466476
returndecoded;
467477
}
468-
elseif (state->decode_buffer+required_space<
469-
state->decode_buffer_head)
478+
elseif (required_space<
479+
state->decode_buffer_head-state->decode_buffer)
470480
{
471-
/* There is space between start and head. */
481+
/*-
482+
* There is space between start and head.
483+
*
484+
* +-----+--------------------+-----+
485+
* |here!|////////////////////| |
486+
* +-----+--------------------+-----+
487+
* ^ ^
488+
* | |
489+
* h t
490+
*/
472491
decoded= (DecodedXLogRecord*)state->decode_buffer;
473492
decoded->oversized= false;
474493
returndecoded;
@@ -477,10 +496,19 @@ XLogReadRecordAlloc(XLogReaderState *state, size_t xl_tot_len, bool allow_oversi
477496
else
478497
{
479498
/* Tail is to the left of head. */
480-
if (state->decode_buffer_tail+required_space<
481-
state->decode_buffer_head)
499+
if (required_space<
500+
state->decode_buffer_head-state->decode_buffer_tail)
482501
{
483-
/* There is space between tail and head. */
502+
/*-
503+
* There is space between tail and head.
504+
*
505+
* +-----+--------------------+-----+
506+
* |/////|here! |/////|
507+
* +-----+--------------------+-----+
508+
* ^ ^
509+
* | |
510+
* t h
511+
*/
484512
decoded= (DecodedXLogRecord*)state->decode_buffer_tail;
485513
decoded->oversized= false;
486514
returndecoded;

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp